The present invention relates to the use of oleamide based analogs that potentiate serotonin receptor subtypes. Some of the analogs are more potent agonists than oleamide and some of the analogs possess dual agonist/antagonist activity. Such analogs may permit selective modulation of or even have opposing effects on different serotonin receptor subtypes.
Oleamide (1) is an endogenous fatty acid primary amide that accumulates in the cerebrospinal fluid under conditions of sleep deprivation and induces physiological sleep in animals (Cravatt et al. (1995) Science 268, 1506-1509; Lerner et al. (1994) Proc. Natl. Acad. Sci. USA 91, 9505-9508; Cravatt et al. (1996) J. Am. Chem. Soc. 118, 580-590). Consistent with its role as a prototypical member of a new class of biological signaling molecules, enzymatic regulation of the endogenous concentrations of oleamide has been described or proposed (Patterson et al. (1996) J. Am. Chem. Soc. 118, 5938-5945; Cravatt et al. (1996) Nature 384, 83-87; Giang et al. Proc. Natl. Acad. Sci. USA 94, 2238-2242; Thomas et al. (1997) J. Neuroscience Res. 50, 1-6; Merkler et al. (1996) Arch. Biochem. Biophys. 330, 430-434).
Fatty acid amide hydrolase (FAAH) is an integral membrane protein that degrades 1 to oleic acid and potent inhibitors of the enzyme have been detailed (Koutek et al. (1994) J. Biol. Chem. 269, 22937-22940; Petrocellis et al. (1997) Biochem. Biophys. Rsch. Commun. 231, 82-88; Deutsch et al. (1997) Biochem. Pharmacol. 53, 255-260). The characterization and neuronal distribution of FAAH have been disclosed and the enzyme was found to possess the ability to hydrolyze a range of fatty acid amides including anandamide which serves as an endogenous ligand for the cannabinoid receptor (Devane et al. (1992) Science 258, 1946-1949; Di Marzo et al. (1995) Prostaglandins, Leukot. Essent. Fatty Acids 53, 1-11). Unlike anandamide, an appealing feature of this new class of biological signaling agents is the primary amide suggesting that their storage and release may be controlled in a manner analogous to that of peptide hormones terminating in a primary amide.
Recent studies have shown the oleamide modulates serotonergic neurotransmission (Huidobro-Toro et al. (1996) Proc. Natl. Acad. Sci. USA 93, 8078-8082; Thomas et al. (1997) Proc. Natl. Acad. Sci. USA 94, 14115-14119). In the first disclosure of such effects, oleamide was shown to potentiate 5-HT2C and 5-HT2A receptor-mediated chloride currents in transfected frog oocytes, but not those elicited by the 5-HT3 ion-gated channel receptor or other G protein coupled receptors. This potentiation was greatest for the 5-HT2C receptor subtype where the effect was observed at concentrations as low as 1 nM and was maximal at 100 nM oleamide. Oleamide did not alter the serotonin (5-HT) EC50 but instead increased receptor efficacy.
Similarly, oleamide has been reported to potentiate phosphoinositide hydrolysis in rat pituitary P11 cells expressing the 5-HT2 receptor but to inhibit 5-HT7 receptor-mediated stimulation of cAMP levels in HeLa cells transfected with the receptor. In these efforts, oleamide was shown to act as a weak agonist at the 5-HT7 receptor but to behave as an unsurmountable antagonist in the presence of serotonin illustrating that it may act at an allosteric site (Huidobro-Toro et al. (1996) Proc. Natl. Acad. Sci. USA 93, 8078-8082; Thomas et al. (1997) Proc. Natl. Acad. Sci. USA 94, 14115-14119). Thus, oleamide has been shown to enhance (5-HT2A, 5-HT2C), disrupt (5-HT7), or have no effect (5-HT3) on serotonergic signal transduction at various receptor subtypes. Serotonin receptors have been implicated in anxiety, depression, appetite, thermoregulation as well as sleep and mood regulation and strong links between 5-HT1, 5-HT2, and 5-HT7, and the regulation of sleep have been disclosed (Leonard et al. (1996) Psychother. Psychosom. 65, 66-75; Lovenberg et al. (1993) Neuron 11, 449-458).
What is needed are analogs which possess inhanced activity and selectivity over that of oleamide for the potentiation of serotonergic signal transduction at various receptor subtypes.
The invention is directed to the use of analogs which potentiate serotonin receptor subtypes. Many of the analogs are more potent agonists than oleamide and some of the analogs possess dual agonist/antagonist activity. Such analogs may permit selective modulation of or even have opposing effects on different serotonin receptor subtypes.
One aspect of the invention is directed to a method for selectively potentiating a cell having a serotonin receptor subtype 5-HT1A. The method employs the step of contacting the cell having the serotonin receptor subtype 5-HT1A with a quantity of serotonergic agent possessing 5-HT1A agonist activity sufficient for potentiating said cell. Preferred serotonergic agents include compounds represented by the structure: 
In the above structure, X is a diradical selected from the group represented by the following structures: 
In the above structures, Z is a radical selected from the group consisting of: xe2x80x94CH2 and O; Y is a diradical selected from the group consisting of: xe2x80x94CH2xe2x80x94, xe2x80x94CH(CH3)xe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94CH(SH)xe2x80x94, xe2x80x94CHSAc)xe2x80x94, xe2x80x94CH(OH)xe2x80x94, xe2x80x94CHClxe2x80x94, xe2x80x94C(xe2x95x90O)xe2x80x94, xe2x80x94C(xe2x95x90O)CH2xe2x80x94, xe2x80x94CH2NHC(xe2x95x90O)xe2x80x94, and xe2x80x94CH2N(CH3)C(xe2x95x90O)xe2x80x94; R1 is a radical selected from the group consisting of: hydrogen, xe2x80x94NH2, OH, MeNHxe2x80x94, Me2Nxe2x80x94, EtNHxe2x80x94, Et2Nxe2x80x94, CH2xe2x95x90CHCH2NHxe2x80x94, n-propyl-NHxe2x80x94, i-propyl-NHxe2x80x94, cyclopropyl-NHxe2x80x94, i-propyl-NMe-, butyl-NHxe2x80x94, pyrrolidine-, phenyl-NHxe2x80x94, phenyl(CH2)3NHxe2x80x94, HONHxe2x80x94, MeONMe-, NH2NHxe2x80x94, CH3Oxe2x80x94, CH3CH2Oxe2x80x94, CH3(CH2)2Oxe2x80x94, Me2CHCH2Oxe2x80x94, Hxe2x80x94, CF3xe2x80x94, BrCH2xe2x80x94, ClCH2xe2x80x94, N2CHxe2x80x94, HOCH2CH2NHxe2x80x94, (HOCH2CH2)2Nxe2x80x94, HOCH2CH2CH2NHxe2x80x94, HOCH2CH(OAc)CH2Oxe2x80x94, and HO2CCH2NHxe2x80x94; R2 is a radical selected from the group consisting of: xe2x80x94CH3, xe2x80x94CH2OCH3, and xe2x80x94CO2H; and is an integer from 0 to 15; m is an integer from 0 to 15 with the requirement that the sum of n+m is an integer from 11 to 15.
Another aspect of the invention is directed to a method for selectively enhancing a serotonergic signal transduction response of a cell having serotonin receptor subtype 5-HT1A. Enhancement is achieved by contacting the cell, in the presence of serotonin, with a quantity of the above serotonergic agent possessing 5-HT1A agonist activity sufficient to selectively enhance the serotonergic signal transduction response of said cell.
Another aspect of the invention is directed to a method for selectively potentiating a cell having a serotonin receptor subtype 5-HT2A. The method employs the step of contacting the cell having the serotonin receptor subtype 5-HT1A with a quantity of a serotonergic agent possessing 5-HT2A agonist activity sufficient to selectively potentiate such cell. Preferred serotonergic agents include compounds represented by the structure: 
In the above structure, X is a diradical selected from the group represented by the following structures: 
In the above structures, Z is xe2x80x94CH2xe2x80x94; Y is a diradical selected from the group consisting of: xe2x80x94CH2xe2x80x94, xe2x80x94CH(CH3)xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94CHClxe2x80x94, xe2x80x94CH2NHC(xe2x95x90O)xe2x80x94, and xe2x80x94CH2N(CH3)C(xe2x95x90O)xe2x80x94; R1 is a radical selected from the group consisting of: hydrogen, xe2x80x94NH2, OH, MeNHxe2x80x94, Me2Nxe2x80x94, EtNHxe2x80x94, Et2Nxe2x80x94, CH2xe2x95x90CHCH2NHxe2x80x94, HONHxe2x80x94, MeONMe-, NH2NHxe2x80x94, CF3xe2x80x94, and ClCH2xe2x80x94; R2 is a radical selected from the group consisting of: xe2x80x94CH3 and xe2x80x94CH2OH; and n is an integer from 0 to 15; m is an integer from 0 to 15 with the requirement that the sum of n+m is an integer from 11 to 15. However, the following provisos apply: if Y is CH2, X is an ethene diradical, R1 is xe2x80x94NH2, and R2 is xe2x80x94CH3, then n cannot be 1 if m is 12; n cannot be 2 if m is 9; n cannot be 4 if m is 9; n cannot be 5 if m is 2, 4, 6, 8, 10 and 12; n cannot be 6 if m is 6; n cannot be 7 if m is 6; and n cannot be 8 if m is 3.
Another aspect of the invention is directed to a method for selectively enhancing a serotonergic signal transduction response of a cell having serotonin receptor subtype 5-HT2A. Enhancement is achieved by contacting the cell, in the presence of serotonin, with a quantity of the above serotonergic agent possessing 5-HT2A agonist activity sufficient to selectively enhance the serotonergic signal transduction response of said cell.
Another aspect of the invention is directed to a method for selectively inhibiting a serotonergic signal transduction response of a cell having serotonin receptor subtype 5-HT1A. Inhibition is achieved by contacting the cell with an inhibitory concentration of a serotonergic agent possessing 5-HT1A antagonist activity. Preferred serotonergic agents having antagonist activity include compounds represented by the structure: 
In the above structure, X is an ethene diradical; Y is a methylene diradical; R1 is a radical selected from the group consisting of xe2x80x94NH2 and cyclopropyl-NHxe2x80x94; and R2 is a radical selected from the group consisting of xe2x80x94CH3, xe2x80x94CH2OH and xe2x80x94CONH2. xe2x80x9cnxe2x80x9d is an integer from 0 to 15; and xe2x80x9cmxe2x80x9d is an integer from 0 to 15 with the requirement that the sum of n+m is an integer from 11 to 15. However, there are two provisos, viz., if R1 is xe2x80x94NH2, then R2 is not xe2x80x94CH3; and if R2 is xe2x80x94CH3, then R1 is not xe2x80x94NH2.
Another aspect of the invention is directed to a method for selectively inhibiting a serotonergic signal transduction response of a cell having serotonin receptor subtype 5-HT2A. Inhibition is achieved by contacting the cell with an inhibitory concentration of a serotonergic agent possessing 5-HT2A antagonist activity. Preferred serotonergic agents having antagonist activity include compounds represented by the structure: 
In the above structure, X is an ethene diradical; Y is a diradical selected from the group consisting of: xe2x80x94CH2xe2x80x94, xe2x80x94C(CH3)2xe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94CH(SH)xe2x80x94, xe2x80x94CH(SAc)xe2x80x94, xe2x80x94CH2NHC(xe2x95x90O)xe2x80x94, and xe2x80x94CH2N(CH3)C(xe2x95x90O)xe2x80x94; R1 is a radical selected from the group consisting of: xe2x80x94NH2, xe2x80x94OH, cyclopropyl-NHxe2x80x94, butyl-NHxe2x80x94, phenyl-NHxe2x80x94, CH3Oxe2x80x94, CH3CH2Oxe2x80x94, N2CHxe2x80x94, and HOCH2CH(OAc)CH2Oxe2x80x94; and R2 is a radical selected from the group consisting of: xe2x80x94CH3, xe2x80x94(CH2)2CH3, xe2x80x94(CH2)4CH3, and xe2x80x94(CH2)6CH3. xe2x80x9cnxe2x80x9d is an integer from 0 to 15; and xe2x80x9cmxe2x80x9d is an integer from 0 to 15 with the requirement that the sum of n+m is an integer from 11 to 15. However, there are two provisos, viz., if R1 is xe2x80x94NH2, then Y is not xe2x80x94CH2xe2x80x94; and if Y is xe2x80x94CH2xe2x80x94, then R1 is not xe2x80x94NH2.
Another aspect of the invention is directed to a method for selectively potentiating a cell having a serotonin receptor subtype 5-HT1A, Selective potentiation is achieved by contacting the cell having the serotonin receptor subtype 5-HT1A with a quantity of a serotonergic agent possessing 5-HT1A agonist activity sufficient to selectively potentiate said cell. Preferred serotonergic agents having selective potentiating activity include linoleamide and a compound represented by one of the following structures: 
The serotonergic signal transduction response of a cell having serotonin receptor subtype 5-HT1A, may also be enhance by contacting the cells with a quantity of the above indicated agents sufficient to enhance the serotonergic signal transduction response.
Another aspect of the invention is directed to a method for selectively potentiating a cell having a serotonin receptor subtype 5-HT2A. Selective potentiation is achieved by contacting the cell having the serotonin receptor subtype 5-HT2A with a quantity of a serotonergic agent possessing 5-HT2A agonist activity sufficient to selectively potentiate said cell. Preferred serotonergic agents having selective potentiating activity include a fatty acid primary amide group consisting of 18:29,12, 20:211,14, 18:36,9,12, 18:39,12,15, 20:38,11,14, 20:311,14,17, 20:55,8,11,14,17, and 22:64,7,10,13,16,19. The serotonergic signal transduction response of a cell having serotorin receptor subtype 5-HT2A, may also be enhance by contacting the cells with a quantity of the above indicated agents sufficient to enhance the serotonergic signal transduction response.